The present invention relates to rotary valves of the type which may be disassembled by the user for easy cleaning.
Rotary vane valves are commonly used as air lock devices for transferring particulate solids between two regions or systems having different pressures. Typical rotary vane valves consist of a closed cylindrical housing with material inlet and outlet openings through the housing lateral wall, and an externally driven rotor unit within the housing, having a number of pockets for transferring the material from the inlet to the outlet.
Such valves have been used in the food and pharmaceutical industries, where the maintenance of sanitary conditions is necessary. Such units are typically chrome or highly polished stainless steel, which can be disassembled for cleaning, i.e., to maintain hygienic conditions and to prevent contamination by the inadvertent mixing of materials from different batch processing operations. In these industries, the units are also typically designed for low pressure and light service, so that disassembly can be quickly accomplished without the use of hand tools.
Recently other industries, such as the plastic industry, has found the need for a rotary valve similar to the type used in the food and pharmaceutical industries, but capable of higher pressure, abrasion resistance, and the handling of larger volumes of feed material. The plastics industry is increasing requiring quick and easy disassembly as well, in part due to their customers' requirements for shorter production runs. Shorter runs means that the major material handling systems must be thoroughly cleaned on a daily or weekly basis. Even if one plastic pellet is missed during such cleaning, the subsequent run is affected by, for example, color streaking in bottles or the like, and excessive scrap relative to the total volume of the production run.
U.S. Pat. No. 4,565,305 illustrates a known type of rotary vane valve. FIG. 1 herein is an exploded view of another known rotary vane valve, showing that the typical construction has the rotor and shaft rigidly connected together as a functional unit. Known improvements to these basic designs, for the purpose of promoting the quick disassembling and cleaning of the rotor, have focused on facilitating the removal of the rotor unit without the need for heavy tools and the like. Nevertheless, although disassembly and cleaning have been facilitated, the reassembly of the complete rotary vane valve has been time-consuming, particularly with respect to the reattachment and alignment of the shaft with the motorized or similar drive device associated with the valve.
Reassembly requires care because rotary vane valves of this type have close axial and radial tolerances in order that the clearance between the vanes and the housing wall can be kept within prescribed limits. Differential thermal expansion affects, the pressure differential across the valve, and particulate size and hardness, all dictate that the vane clearance range be maintained after disassembly and reassembly. Moreover, disassembly and correctly aligned reassembly should be readily accomplished by the user of the valve, thereby avoiding down time associated with calling in a mechanic or equipment maintenance man.